This invention primarily relates to a knife having a sliding blade which automatically locks in an extended or retracted position and which is operable with one hand.
The typical pocket knife is a folding knife which requires two-handed operation. The user must hold the handle of the knife with one hand while the other hand is used to manipulate the blade in order to extract the blade from the handle and pivot it outwardly to an extended, operating position. Once the blade is extended to the operating position, many knives lack a feature which locks the blade in such a position. Accordingly, the knife blade could inadvertently close on the fingers of the user if the user does not exercise proper care. Additionally, when such folding knives are in their retracted state, it is often difficult for the user to get the tip of his or her finger or fingernail against the blade in a manner sufficient to pull the blade out from the handle because of the only slight extension of the blade from the handle when the blade is in its retracted state. This can make for difficult or time consuming opening of the blade from the handle.
Also, and importantly, conventional folding knives cannot typically be operated with one hand in an easy manner. Accordingly, if a user has one hand occupied, the user must stop what he or she is doing with that hand in order to open a knife. This can become especially critical in emergency situations when only one hand is available and also for rescue personnel who may be required to exert a force with one hand while reaching for and opening a sharpened knife with the other.
Knives having sliding blades which can be opened with one hand have been disclosed in the past. For example, U.S. Pat. No. 4,926,555, issued to Lemaire, discloses a pocket knife having a button which is pivotally connected to a blade. Rearward pivoting of the button depresses a leaf spring to allow for retraction of the blade within a handle. U.S. Pat. No. 292,917, issued to Kaldenbach, discloses a pocket knife having a push pin which is grasped for moving the knife blade out of the knife. When the push pin reaches an enlarged portion of the guide slot, the push pin is pushed outwardly, thereby locking the blade. U.S. Pat. No. 2,474,609, issued to Wolf, discloses a knife having a blade with a push button provided on a shank of the blade. A spring is attached to the blade, such that when the push button is moved forward, such movement works against the spring. Upon release of the push button, the knife is pulled back into the sheath by the spring.
Other designs disclosed include U.S. Pat. No. 4,592,140, issued to Chasen, which discloses a combination food peeler and slicer having a thumb operating portion which is depressed in order to advance a blade from a handle. U.S. Pat. No. 2,552,945, issued to Eaton, et al., discloses a pocket knife having a latch member which seats in openings for locking the blade in a partially extended, or extended, position, respectively. U.S. Pat. No. 1,888,887, issued to Readman, discloses a pocket knife having a plunger which is depressed by a spring biased finger to a position below longitudinally extending flanges having notches therein. The blade of the knife is locked by releasing the finger, which causes the plunger to engage with a notch in the flanges. French Patent No. 1,122,971, British Patent No. 5,487 and U.S. Pat. No. 317,208, disclose handle-mounted pivotal levers which lock the blade from accidental retraction back into the knife handle.
While prior knife designs having blades which slide between a retracted position and an extended position are available, they present limitations which may interfere with providing a simple, low profile, fast-opening and secure device.